1. Field of the Invention
The present invention relates to a reel for a metal linear material. More particularly, the present invention relates to a reel for a metal linear material suitable as a reel for winding a fine metal linear material, such as a reel for unwinding a filament for a tire cord in a twisting machine for a tire cord, a reel for winding a saw wire in a wire saw, and the like.
2. Description of the Related Art
Metal linear material reels for winding a fine metal linear material, such as a filament for a tire cord, a saw wire, or the like, are typically formed of a thick steel material. The reels are divided, depending on how they are manufactured, into an integrally formed reel (machined reel) obtained by integrally machining a winding drum portion and flange portions from a steel material, a welded reel obtained by separately producing a winding drum portion and flange portions from a steel material and integrating the winding drum portion and the flange portions together by welding, an assembled reel obtained by separately producing a winding drum portion and flange portions from a steel material and joining the winding drum portion and the flange portions together using bolts, and the like (see, for example, JP 2002-370152A). However, when these reels made of a thick steel material are used for fine metal linear materials, it is necessary to further increase the thickness of the winding drum portion and the flange portions so as to secure sufficient strength and rigidity, and in some cases, the joint portions of the winding drum portion and the flange portions need to be reinforced and the winding drum portion itself needs to be reinforced, resulting in a considerable increase in the weight of the reel, leading to a problem with handling, an increase in transportation cost, and also an increase in material cost and machining cost.
Regarding the metal linear material reel, when a fine metal line, for example, a fine metal line having a line diameter of about 0.15 to 0.40 mm which is used as a filament for a steel cord (tire cord) for reinforcement of rubber products, or an ultra-fine metal line (saw wire) for a wire saw having a line diameter of 0.12 to 0.16 mm or less is wound around the reel with a predetermined tension (e.g., 0.4 to 1.5 kg), a large winding pressure (squeezing force) is applied to the winding drum portion due to the winding tension. In addition, when a number of layers of the fine metal line are wrapped around the reel, a lateral pressure (flaring force) is applied to the flange portions. The winding pressure (squeezing force) and the lateral pressure (flaring force) applied to the winding drum portion acceleratedly increase with a decrease in the line diameter of the wound metal linear material, a decrease in the winding pitch, an increase in the winding tension, and an increase in the number of layers of the wound metal linear material.
Therefore, in the reel around which such a fine metal linear material is wound, the winding drum portion needs to have sufficient strength and rigidity against the winding pressure (squeezing force) and expansion caused by the lateral pressure flaring the flanges, and the flange portions needs to have sufficient strength against the lateral pressure and sufficient rigidity against flexure due to the lateral pressure. The flexure of the flange due to the lateral pressure causes deformation (dent) of the winding drum portion, and the deformation of the winding drum portion leads to hunting when the wire is wound, which may cause cutting of the wire.
Particularly, in the case of a “slim type reel” in which the height of the flange portions is larger than the width of the winding drum portion, the winding pressure applied to the winding drum portion is much larger than the pressure (lateral pressure) applied to the flange portions. Therefore, the pressure applied to the flange portions flares both the flange portions, i.e., the flange portions go away from each other at the outer edges. The lateral pressure may reach several tons or several tens of tons when a saw wire is wound around a wire saw reel in an amount corresponding to a weight of 40 to 60 kg or more. In this case, as a result, stress is concentrated to corners which are joint portions between the winding drum portion and the flange portions, likely leading to occurrence of damage in these portions. On the other hand, in the case of a “long drum reel” in which the width of the winding drum portion is larger than the diameter of the flange portions, a pressure caused by the winding tension is concentrated to the winding drum portion, so that the winding pressure (squeezing force) applied to the winding drum portion increases. Due to this large winding pressure (squeezing force), the winding drum portion is deformed such that the diameter of a middle portion of the winding drum portion shrinks. This deformation causes both flange portions to fall inward. In the case of such a reel, damage is likely to occur in the winding drum portion.
Thus, conventional reels made of a thick steel material do not achieve a reduction in weight while securing strength and rigidity sufficient as a reel for a fine metal linear material which is used particularly for a twisting machine for a tire cord, or a wire saw.
Therefore, a metal linear material reel capable of reducing the weight while securing the strength and rigidity, has been developed in which flanges having swelling reinforcing ribs which are formed on an outer surface by presswork of a high-tensile steel sheet, and a hollow ring-shaped outer edge reinforcing portion which is formed by bending back the outer edge, are fixedly joined to both ends of a winding drum by welding (see, for example, JP 9-295768A).
When a light-weight fine metal linear material, such as a filament for a tire cord, a saw wire, or the like, is wound around the above-described reel in which flanges having swelling reinforcing ribs which are formed on an outer surface by presswork of a high-tensile steel sheet, and a hollow ring-shaped outer edge reinforcing portion which is formed by bending back the outer edge, are fixedly joined to both ends of a winding drum by welding, the strength and rigidity are sufficient to withstand the winding weight to some extent. However, the hollow ring-shaped outer edge reinforcing portion provided so as to prevent deformation of the flange outer edge portion due to a shock when, for example, the collars of reels strike each other during transportation has a substantially circular cross-section, so that the flange has a round inner surface at the outer edge, and therefore, a substantially flat portion of the flange is reduced. As a result, the amount of a metal linear material wound around the reel is reduced, though a metal linear material can be wound up to the very outer edge of the flange in machined reels and the like.